From The Imaginative Conservative
“Under the Law, says Aquinas, whenever foreigners wished to be admitted into complete fellowship with the Israelites, “a certain order was observed:
…”For they were not at once admitted to citizenship: just as it was law with some nations that no one was deemed a citizen except after two or three generations, as the Philosopher says” (Politics III, 2).
The reason for this was that if foreigners were allowed to meddle with the affairs of a nation as soon as they settled down in its midst, many dangers might occur, since the foreigners not yet having the common good firmly at heart might attempt something hurtful to the people.
In other words, according to precepts Aquinas cites as “suitable” (convenientia) for directing relations “with foreigners” (extraneis), only the descendants of new arrivals would be eligible for citizenship. The reason for this seems to be that the Israelites understood true assimilation into a living community to be a profound, challenging process, one requiring not years, nor even decades, but generations. And lest we miss a couple of other important implicit points, note that the would-be citizens here are presumably not participating in massive overwhelming waves of illegal settlement and that their hearty espousal of Israelite customs, heritage, and language seems to have been taken for granted…” —Jerry Salyer
— Why the Irish Support Palestine. Remarkable similarities of history.